1. Field of the Invention
The present invention relates generally to marine autopilot apparatus and, more particularly, to a marine autopilot apparatus having an alarm system to collectively indicate the occurrence of abnormality relating to the rudder control loop by an independent alarm indicator lamp.
2. Description of the Prior Art
Recently, marine autopilot apparatus has been provided with a microcomputer to fulfill various requirements, such as, to achieve energy-saving steering, to save man power, to increase steering efficiency and so on. In such marine autopilot apparatus, the microcomputer carries out various control functions relating to the automatic steering. Also, the microcomputer performs the processing of various alarm signals such as the detection of an occurrance of abnormality of each alarm point, the recovery from the abnormality, as well as the indication of the alarm point at which the abnormality occurred and so on.
Meanwhile, the latest alarm indication systems have been modified so that:
Since the microcomputer is incorporated into the marine autopilot system, an indication system is provided having an independent alarm indicator lamp exclusively located at each alarm point to individually indicate the situation of the alarms. However, the system is provided with only one general alarm indicator lamp to representationally indicate the presence or absense of an alarm point at which an abnormality occurred. As to the individual indication of alarm points where abnormality occurred, they are individually indicated on a general-purpose indicator which is adapted to indicate various data, values set and so on within the marine autopilot apparatus as a kind of indication data.
FIG. 1 is a block diagram showing an example of this kind of a known alarm system.
Referring to FIG. 1, an alarm point condition signal 10 is shown to indicate a normal condition or abnormal condition by making itself high (H) or low (L) in level or vice versa. The alarm point condition signal 10 contains a rudder control system alarm point condition signal 11 which indicates the normal condition or abnormal condition of a rudder servo amplifier 2, a power unit 60 or the like. The rudder servo amplifier 2 and the power unit 60 are each adapted to control a steering machine 70. The rudder servo amplifier 2 generates a power unit drive signal 61 which is then supplied to the power unit 60, while the power unit 60 generates a follow-up signal 62 which is then supplied to the rudder servo amplifier 2. Thus, the rudder servo amplifier 2 and the power unit 60 constitute a servo loop.
Meanwhile, there is shown a microcomputer 1 which is adapted to detect from the input alarm point condition signal 10 the occurences of abnormality at every alarm point (the change of the signal from the normal condition to the abnormal condition) and the recovery of the abnormal condition to the normal condition (the change of the signal from the abnormal condition to the normal condition) at every alarm point. The microcomputer 1 is adapted if there exists even one abnormal alarm point, to cause the representing alarm indicator lamp 20 to be lit or blinked to indicatre the existence of the abnormal alarm point. Further, if an abnormality newly occurs or it is requested to indicate the abnormal alarm point, the microcomputer 1 causes a general-purpose indicator 30 to indicate the name or the like of the abnormal alarm point. The general-purpose indicator 30 may, in most cases, be an indicator which can indicate English alphabets and numerals of about 10 to 40 letters. Since this type of indicator 30 indicates only one or two alarm points at the same time, if it is necessary to indicate more than two alarm points, the indication must be renewed by a switch or other operation.
FIG. 2 illustrates an example of the representing alarm indicator lamp 20 in which the lamp 20 is formed of an emergency alarm indicator lamp 21 and a warning indicator lamp 22. In this case, when an alarm occurs which requires urgent operations, such as, switching the automatic steering mode of the ship to the mamual steering mode or to the non-follow-up steering mode and so on, the emergency alarm indicator lamp 21 is caused to be lit or blinked. When another alarm is generated, the warning indicator lamp 22 is caused to be lit or blinked. According to the representing alarm indicator lamp 20 of FIG. 2, the generated alarms are classified in accordance with the degree of emergency and then indicated.
However, according to the known marine autopilot apparatus as described above, the abnormality at the alarm point is collectively detected by the microcomputer 1 and the conditions that produce the alarms are indicated solely or in the classied forms corresponding to the emergency degree of several stages of alarms on the representing alarm indicator lamp 20. Also, the content of the individual alarm is sequentially indicated on the general-purpose indicator 30 at every one or two points by the name of alarm or the like. Accordingly, when an alarm is generated, the occurrence of the alarm and the degree of emergency of the alarm can be immediately known on the representing alarm indicator lamp 20. In this case, however, the meaning of the alarm can not be, practically, checked immediately because the alarm contents must be sequentially indicated on the general-purpose indicator 30 and confirmed one by one by the user. In other words, when the emergency alarm indicator lamp 21 is lit during the automatic steering, it is impossible for the user to immediately judge whether the urgent corrective operation is the switching operation from the automatic steering to the manual steering or the switching for the rudder control system because of trouble occurring in the rudder control loop. Thus, a lot of time is required until the user carries out the proper urgent operation for the alarm. This prolongs the abnormal condition during which the steering is disabled or that the steering function is lowered, thus increasing a risk in steering.
Further, if trouble occurs in the general-purpose indicator 30, the alarm content can be separately indicated, so that the content of the alarm can not be known. Accordingly, even when the urgent operation must be done immediately, such operation can not be done properly. Particularly when trouble occurs in the microcomputer 1, the alarm function itself is disabled so that during the manual steering or non-follow-up steering which should be functional regardless of the condition of the autopilot system controlled by the microcomputer 1, it becomes impossible to know an abnormality even if it occurs in the rudder control loop.